The gut-to-brain axis for toxin-induced defensive responses.

After ingestion of toxin-contaminated food, the brain initiates a series of defensive responses (e.g., nausea, retching, and vomiting). How the brain detects ingested toxin and coordinates diverse defensive responses remains poorly understood. Here, we developed a mouse-based paradigm to study defensive responses induced by bacterial toxins. Using this paradigm, we identified a set of molecularly defined gut-to-brain and brain circuits that jointly mediate toxin-induced defensive responses. The gut-to-brain circuit consists of a subset of Htr3a+ vagal sensory neurons that transmit toxin-related signals from intestinal enterochromaffin cells to Tac1+ neurons in the dorsal vagal complex (DVC). Tac1+ DVC neurons drive retching-like behavior and conditioned flavor avoidance via divergent projections to the rostral ventral respiratory group and lateral parabrachial nucleus, respectively. Manipulating these circuits also interferes with defensive responses induced by the chemotherapeutic drug doxorubicin. These results suggest that food poisoning and chemotherapy recruit similar circuit modules to initiate defensive responses.

The Evf2 Ultraconserved Enhancer lncRNA Functionally and Spatially Organizes Megabase Distant Genes in the Developing Forebrain.

Gene regulation requires selective targeting of DNA regulatory enhancers over megabase distances. Here we show that Evf2, a cloud-forming Dlx5/6 ultraconserved enhancer (UCE) lncRNA, simultaneously localizes to activated (Umad1, 1.6 Mb distant) and repressed (Akr1b8, 27 Mb distant) chr6 target genes, precisely regulating UCE-gene distances and cohesin binding in mouse embryonic forebrain GABAergic interneurons (INs). Transgene expression of Evf2 activates Lsm8 (12 Mb distant) but fails to repress Akr1b8, supporting trans activation and long-range cis repression. Through both short-range (Dlx6 antisense) and long-range (Akr1b8) repression, the Evf2-5'UCE links homeodomain and mevalonate pathway-regulated enhancers to IN diversity. The Evf2-3' end is required for long-range activation but dispensable for RNA cloud localization, functionally dividing the RNA into 3'-activator and 5'UCE repressor and targeting regions. Together, these results support that Evf2 selectively regulates UCE interactions with multi-megabase distant genes through complex effects on chromosome topology, linking lncRNA-dependent topological and transcriptional control with interneuron diversity and seizure susceptibility.

HTR3A Promotes Non-small Cell Lung Cancer Through the FOXH1/Wnt3A Signaling Pathway.

5-Hydroxytryptamine receptors (5-HTRs) are strongly correlated with tumor progression in various types of cancer. Despite this, the underlying mechanisms responsible for the role of 5-HTRs in non-small cell lung cancer (NSCLC) remains unclear. This study aimed to investigate the relationship between 5-hydroxytryptamine receptor 3A (HTR3A) and NSCLC development. Our findings indicated a higher distribution of HTR3A expression in NSCLC tissues when compared with normal tissues, where patients with high HTR3A levels demonstrated shorter overall survival times. In vitro analyses revealed that overexpression of HTR3A facilitated the proliferation and migration of NSCLC cell lines (A549 and NCI-H3255). Similarly, a notable acceleration of tumor growth and enhanced pulmonary tumorigenic potential were observed in HTR3A-overexpressing tumor-bearing mice. Mechanistically, upregulation of Forkhead Box H1 (FOXH1) by HTR3A led to the activation of Wnt3A/ß-catenin signaling pathways, thereby promoting the development of NSCLC. Our report thus highlights the significance of the HTR3A/FOXH1 axis during tumor progression in NSCLC, proposing HTR3A as a possible diagnostic indicator and candidate target for clinical therapy.

5-HT3 Signaling Alters Development of Sacral Neural Crest Derivatives That Innervate the Lower Urinary Tract.

The autonomic nervous system derives from the neural crest (NC) and supplies motor innervation to the smooth muscle of visceral organs, including the lower urinary tract (LUT). During fetal development, sacral NC cells colonize the urogenital sinus to form pelvic ganglia (PG) flanking the bladder neck. The coordinated activity of PG neurons is required for normal urination; however, little is known about the development of PG neuronal diversity. To discover candidate genes involved in PG neurogenesis, the transcriptome profiling of sacral NC and developing PG was performed, and we identified the enrichment of the type 3 serotonin receptor (5-HT3, encoded by Htr3a and Htr3b). We determined that Htr3a is one of the first serotonin receptor genes that is up-regulated in sacral NC progenitors and is maintained in differentiating PG neurons. In vitro cultures showed that the disruption of 5-HT3 signaling alters the differentiation outcomes of sacral NC cells, while the stimulation of 5-HT3 in explanted fetal pelvic ganglia severely diminished neurite arbor outgrowth. Overall, this study provides a valuable resource for the analysis of signaling pathways in PG development, identifies 5-HT3 as a novel regulator of NC lineage diversification and neuronal maturation in the peripheral nervous system, and indicates that the perturbation of 5-HT3 signaling in gestation has the potential to alter bladder function later in life.

HTR3A is correlated with unfavorable histology and promotes proliferation through ERK phosphorylation in lung adenocarcinoma.

Lung cancer is the leading cause of cancer death around the world. Adenocarcinoma is the most common histological type and has various histologic subtypes: lepidic, acinar, papillary, solid, and invasive mucinous adenocarcinoma. Histologic subtypes are related to invasiveness of tumors; eg, lepidic subtype is less invasive than acinar/papillary subtype. HTR3A is the main subunit of 5-hydroxytryptamine 3 (5-HT3) receptors, which are the only ligand-gated ion channels in seven families of 5-HT receptors. Although 5-HT3 receptor is expressed mainly throughout the central and peripheral nervous systems, some papers report the effect of 5-HT3 receptors on tumor cells, including lung cancer. However, whether HTR3A correlates with histopathological findings such as the histologic subtypes or the distribution in an individual sample remains unclear. Immunohistochemically, we revealed that the higher expression level of HTR3A was detected in acinar, papillary, and solid adenocarcinoma than in adenocarcinoma in situ and lepidic adenocarcinoma; the former was a more aggressive subtype than the latter. We also showed the relationship between HTR3A expression and Ki-67 positivity, widely used as a proliferation marker. Moreover, we generated HTR3A-knockdown lung adenocarcinoma cells and showed that the HTR3A knockdown attenuated proliferation by ERK phosphorylation. Our results indicated that HTR3A expression was related to proliferation in lung adenocarcinoma, by means of both in vitro and immunohistochemical assays on clinical samples. We showed the therapeutic potential of a 5-HT3 receptor antagonist, tropisetron, for the treatment of lung adenocarcinoma.

5'UTR polymorphism in the serotonergic receptor HTR3A gene is differently associated with striatal Dopamine D2/D3 receptor availability in the right putamen in Fibromyalgia patients and healthy controls-Preliminary evidence.

BACKGROUND: Extensive literature has investigated the role of serotonin (5-HT) in the control of the central dopamine (DA) systems, and their dysfunction in the pathological conditions. 5-HT stimulates the local DA release in striatal regions via activation of various receptors including serotonin receptor-3 (5-HT3). Several studies have related polymorphisms (SNPs) in the serotonin receptor-3 (HTR3) genes to be associated with the pain modulation and endogenous pain suppression. A few studies suggested a functional role of 5'UTR SNP in the serotonergic receptor HTR3A gene (rs1062613) in the development of the chronic pain and Fibromyalgia syndrome (FMS) in particular. Here, we investigated the effect of a 5'UTR SNP in the serotonergic receptor HTR3A gene (rs1062613) on striatal dopamine D2/D3 receptor (DRD2) availability and reward-associated DA release in response to unpredictable monetary rewards in 23 women with FMS and 17 age-matched healthy female controls. Furthermore, we aimed to examine if SNP rs1062613 is associated with thermal pain and pain tolerance thresholds. METHODS: We used PET and [11 C]raclopride to assess the DRD2 availability. In the same participants we used the [11 C]raclopride PET bolus-plus-infusion method to measure the [11 C]raclopride receptor binding potential (ΔBP) between an unpredictable reward condition and a sensorimotor control condition. DRD2 availability and ΔBP were assessed in MRI-based striatal regions of interest. Thermal pain and pain tolerance thresholds were assessed outside the scanner. RESULTS: The frequency of SNP rs1062613 genotype differed significantly between groups, indicating that CC homozygotes were more frequent in FMS patients (82.6%) than in healthy controls (41.3%). Our results showed a significant main effect of SNP rs1062613 on [11 C]raclopride binding potential in the right caudate nucleus indicating a higher DRD2 receptor availability for CC-genotype of this SNP. Furthermore, we found a significant group × SNP interaction on [11 C]raclopride binding potential in the right putamen, indicating a higher DRD2 availability in T-carriers compared to CC genotype of SNP rs1062613 in FMS patients, whereas this effect was not present in healthy controls. However, we did not find an influence of SNP rs1062613 on reward-related DA release. In addition, there was no association between SNP rs1062613 and pain threshold or pain tolerance threshold in our data. CONCLUSION: These preliminary results indicate that SNP rs1062613 in the serotonergic receptor HTR3A gene possibly modulates the DRD2 receptor availability.

Evaluation of serotonin receptors (5HTR2A and 5HTR3A) mRNA expression changes in tumor of breast cancer patients.

Background: Several studies have proven the pattern of neurotransmitters, especially serotonin, in carcinogenesis and tumor development. Several studies have also shown that changes in serotonin receptors, especially 5HTR2A and 5HTR3A, can play an important role in incidence of cancers. This study was conducted to investigate changes in mRNA expression of 5HTR2A and 5HTR3A receptors in the breast tumor tissue compared to their marginal zone. Methods: In this study, tissue samples were obtained from 40 female patients with breast cancer. Entire RNA was obtained from the tissues and cDNA synthesis was performed. Finally, real ime PCR technique was performed to investigate the gene expression variation of both 5HTR2A and 5HTR3A. To analyze the results of real time PCR, both ΔΔCt and 2-ΔΔCt equations were used. All statistical analyses were performed using the SPSS 18 software and R-Studio 1.0.136. P values less than 0.05 (p<0.05) and 0.001 (p<0.001) were considered statistically significant. Results: The results showed increased expression of 5HTR2A and 5HTR3A genes in tumoral tissues of patients with breast cancer compared to their marginal tissues, where the 5HTR2A and 5HTR3A genes expression in tumor tissue was 3.12 and 3.24 times more than that of the marginal zone, respectively. Conclusion: The results indicated an increase in the mRNA expression of serotonin receptors (5HTR2A and 5HTR3A) in the tumor tissue compared to the marginal zone, which due to the mitogenic nature of these receptors, is likely to induce more proliferation of cancer cells.

Single-cell RNA-Seq characterization of anatomically identified OLM interneurons in different transgenic mouse lines.

Inhibitory GABAergic interneurons create different brain activity patterns that correlate with behavioural states. In this characterizing study, we used single-cell RNA-Seq to analyse anatomically- and electrophysiologically identified hippocampal oriens-lacunosum moleculare (OLM) interneurons. OLMs express somatostatin (Sst), generate feedback inhibition and play important roles in theta oscillations and fear encoding. Although an anatomically- and biophysically homogenous population, OLMs presumably comprise of two functionally distinct types with different developmental origins, inferred from the expression pattern of serotonin type-3a (5-HT3a, or Htr3a) receptor subunit and 5-HT excitability in a set of OLMs. To broadly characterize OLM cells, we used the Sst-Cre and the BAC transgenic Htr3a-Cre mouse lines and separately analysed SstCre-OLM and Htr3aCre-OLM types. We found a surprisingly consistent expression of Npy in OLMs, which was previously not associated with the identity of this type. Our analyses furthermore revealed uniform expression of developmental origin-related genes, including transcription factors and neurexin isoforms, without providing support for the current view that OLMs may originate from multiple neurogenic zones. Together, we found that OLMs constitute a highly homogenous transcriptomic population. Finally, our results revealed surprisingly infrequent expression of Htr3a in only ~10% of OLMs and an apparently specific expression of the 5-HT3b subunit-coding gene Htr3b in Htr3aCre-OLMs, but not in SstCre-OLMs. However, additional in situ hybridization experiments suggested that the differential expression of Htr3b may represent an unexpected consequence arising from the design of the Htr3a-Cre BAC transgenic line.

ß-Cell adaptation in pregnancy.

Pregnancy in placental mammals places unique demands on the insulin-producing ß-cells in the pancreatic islets of Langerhans. The pancreas anticipates the increase in insulin resistance that occurs late in pregnancy by increasing ß-cell numbers and function earlier in pregnancy. In rodents, this ß-cell expansion depends on secreted placental lactogens that signal through the prolactin receptor. Then at the end of pregnancy, the ß-cell population contracts back to its pre-pregnancy size. In the current review, we focus on how glucose metabolism changes during pregnancy, how ß-cells anticipate these changes through their response to lactogens and what molecular mechanisms guide the adaptive compensation. In addition, we summarize current knowledge of ß-cell adaptation during human pregnancy and what happens when adaptation fails and gestational diabetes ensues. A better understanding of human ß-cell adaptation to pregnancy would benefit efforts to predict, prevent and treat gestational diabetes.

Association Study of Serotonin 3 Receptor Subunit Gene Variants in Antipsychotic-Induced Weight Gain.

BACKGROUND: Schizophrenia (SCZ) is a chronic severe neuropsychiatric disorder, where pharmacological treatment has been hindered by adverse effects, including antipsychotic-induced weight gain (AIWG) and related complications. Genetic studies have been exploring the appetite regulation and energy homeostasis pathways in AIWG with some promising leads. The serotonin system has been shown to participate in these pathways. METHODS: In the current study, we examined single nucleotide polymorphisms across the serotonin receptor genes HTR3A and HTR3B. Prospective weight change was assessed for a total of 149 SCZ patients of European ancestry. RESULTS: We did not find the tested HTR3A or HTR3B gene markers to be associated with AIWG in our sample. CONCLUSION: Our preliminary findings suggest that these receptors may not play a major role in predicting AIWG.